1. Field of the Invention
The present invention relates to a semiconductor photo-sensor having a photo-electric conversion element for converting an incident light to an electrical signal sealed by light transmitting resin, and a method for manufacturing the same.
2. Related Background Art
A prior art photo-electric converter for converting an incident light beam to an electrical signal is shown in FIG. 1.
A photo-electric conversion element 1 is fixed on a photo-electric conversion element support member 2, fine metal wires 3 are wire-bonded at predetermined areas on the photo-electric conversion element 1 and lead terminals 2', and light transmitting resin 4 is molded to form an outer shape. Then, external leads 2" of the lead terminals 2' are cut to a desired length and bent to complete the semiconductor photo-sensor.
The above prior art semiconductor photo-sensor has the following problems.
(1) When a photo-sensing area of the photo-electric conversion element comprises a plurality (n) of photo-sensing cells, if light 6 having a uniform light flux on each of n photo-sensing cells of the photo-electric conversion element 1 is applied, electrical signals derived from the n photo-sensing cells should be of the same level, but they are, in actuality, not of the same level. When light is applied to one of n photo-sensing cells and no light is applied to other photo-sensing cells, an electrical signal which is larger than a dark current is produced by the photo-sensing cell to which the light is not applied. PA1 (2) If there is a defect on the surface 9 of the light transmitting resin 4, an electrical signal from a photo-sensing cell in the vicinity of an area 10 on the photo-electric conversion element 1 to which the light passing through the defect reaches, is lowered. PA1 (1) When the light transmitting resin is molded, mold releasing agent may be deposited on the surface of the resin or a flow is formed during transfer of the mold. They are factors of impeding the light transmission and effect to the photo-characteristic of the photo-electric conversion element. Washing and polishing process to remove them are additionally required, which is a cause to increase a manufacturing cost. PA1 (2) When the optical filter is bonded, liquid bonding material is used. Accordingly, it is difficult to improve a vertical positional precision. In order to improve a horizontal positional precision, mechanical or optical position detection is required. If it is done by a mechanical unit, it is complex and needs expensive investiment. PA1 (3) If an air bubble exists in the bonding material, it impedes the light transmission and effects to the photo-characteristic of the photo-electric conversion element. Accordingly, great care must paid in bonding the optical filter. PA1 (4) As shown in FIG. 12, when the optical filter is a lens 29, the bonding surface of the light transmitting resin 4 is not planar. Accordingly, the light transmitting resin 4 may have an acute corner 30. In such a case, it is hard to release the mold and a crack may be produced in the resin. This lowers the manufacturing yield. PA1 mounting a light transmitting member at a predetermined position on a mold; PA1 holding a semiconductor photo-sensor element comprising a photo-electric conversion element, electrical connection means and lead terminals excluding external leads, in facing relation to the light transmitting member; PA1 injecting light transmitting resin into the mold to seal the semiconductor sensor element and bonding the light transmitting member by the sealant.
Those problems are serious, particularly in a semiconductor photo-sensor for focussing a camera (AF sensor) which has a number of fine photo-sensing cells because the smaller the area per photo-sensing area is, the higher sensitivity is required. Accordingly, it is generally recognized that packaging by the light transmitting resin is inapplicable to the AF sensor.
In another prior art semiconductor photo-sensor, an infrared ray blocking filter is mounted on a light transmission surface of the light transmitting resin. In such a semiconductor photo-sensor, in addition to the above-mentioned problem that the electrical signals which exactly represent the incident light are not produced, the following manufacturing problem arises.